{"item": {"cve_id": "CVE-2021-43890", "ghsa_id": "", "osv_id": "", "title": "Windows AppX Installer Spoofing Vulnerability", "description": "We have investigated reports of a spoofing vulnerability in AppX installer that affects Microsoft Windows. Microsoft is aware of attacks that attempt to exploit this vulnerability by using specially crafted packages that include the malware family known as Emotet/Trickbot/Bazaloader.\nAn attacker could craft a malicious attachment to be used in phishing campaigns. The attacker would then have to convince the user to open the specially crafted attachment. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.\nPlease see the Security Updates table for the link to the updated app. Alternatively you can download and install the Installer using the links provided in the FAQ section.\nPlease see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability.\nDecember 27 2023 Update:\nIn recent months, Microsoft Threat Intelligence has seen an increase in activity from threat actors leveraging social engineering and phishing techniques to target Windows OS users and utilizing the ms-appinstaller URI scheme.\nTo address this increase in activity, we have updated the App Installer to disable the ms-appinstaller protocol by default and recommend other potential mitigations.", "published_at": "2021-12-15T15:15:11.207", "modified_at": "2026-08-06T05:16:36.653", "vendor": "Microsoft", "product": "App Installer", "affected_versions": ["1.0.0.0"], "fixed_versions": [], "cvss_score": 7.1, "cvss_version": "3.1", "cvss_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H", "severity": "HIGH", "epss_score": 0.10295, "epss_percentile": 0.95578, "epss_date": "2026-10-06", "is_kev": true, "kev_date": "2021-12-15", "kev_due_date": "2021-12-29", "kev_action": "Apply updates per vendor instructions.", "cwe_ids": [], "attack_vector": "NETWORK", "attack_complexity": "HIGH", "privileges_required": "LOW", "user_interaction": "REQUIRED", "references": ["https://github.com/ChrisTitusTech/winutil/pull/26", "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html", "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/", "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/", "https://github.com/ChrisTitusTech/winutil/pull/26", "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html", "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/", "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/", "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890"], "source_urls": {"NVD": "https://nvd.nist.gov/vuln/detail/CVE-2021-43890", "CVE.org": "https://www.cve.org/CVERecord?id=CVE-2021-43890", "CISA": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890", "FIRST EPSS": "https://api.first.org/data/v1/epss?cve=CVE-2021-43890"}, "patch_available": null, "workaround_available": null, "sources": ["NVD", "CVE.org", "CISA", "FIRST EPSS"], "reference_items": [{"url": "https://github.com/ChrisTitusTech/winutil/pull/26", "tags": ["Issue Tracking"], "source": "NVD", "name": ""}, {"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "tags": ["Patch", "Vendor Advisory"], "source": "NVD", "name": ""}, {"url": "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html", "tags": ["Press/Media Coverage", "Third Party Advisory"], "source": "NVD", "name": ""}, {"url": "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/", "tags": ["Press/Media Coverage", "Third Party Advisory"], "source": "NVD", "name": ""}, {"url": "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/", "tags": ["Exploit", "Vendor Advisory"], "source": "NVD", "name": ""}, {"url": "https://github.com/ChrisTitusTech/winutil/pull/26", "tags": ["Issue Tracking", "x_transferred"], "source": "NVD", "name": ""}, {"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "tags": ["Patch", "Vendor Advisory", "x_refsource_MISC", "x_transferred"], "source": "NVD", "name": ""}, {"url": "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html", "tags": ["Press/Media Coverage", "Third Party Advisory", "x_transferred"], "source": "NVD", "name": ""}, {"url": "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/", "tags": ["Press/Media Coverage", "Third Party Advisory", "x_transferred"], "source": "NVD", "name": ""}, {"url": "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/", "tags": ["Exploit", "Vendor Advisory", "x_transferred"], "source": "NVD", "name": ""}, {"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890", "tags": ["US Government Resource", "government-resource"], "source": "NVD", "name": ""}], "cvss_v4_score": null, "cvss_v4_vector": "", "cvss_v4_severity": "", "nvd_status": "Analyzed", "cna": "microsoft", "date_reserved": "2021-11-16T00:00:00.000Z", "ssvc": {"options": {"Exploitation": "active", "Automatable": "no", "Technical Impact": "total"}, "version": "2.0.3", "timestamp": "2021-12-14T00:00:00+00:00", "role": "CISA Coordinator"}, "affected_products": [{"vendor": "Microsoft", "product": "App Installer", "ranges": ["avant 1.16", "avant 1.11"], "first_unaffected": ["1.16", "1.11"], "source": "NVD"}], "kev_name": "Microsoft Windows AppX Installer Spoofing Vulnerability", "kev_short_description": "Microsoft Windows AppX Installer contains a spoofing vulnerability which has a high impacts to confidentiality, integrity, and availability.", "kev_ransomware": "Known", "kev_notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-43890", "kev_cwes": [], "wordfence_id": "", "mentions_sources": [], "version_match": "unknown", "risk_score": 55, "risk_class": "Important", "impact": {"confidentialite": "élevé", "integrite": "élevé", "disponibilite": "élevé", "summary": "Un attaquant exploitant cette vulnérabilité pourrait, selon les conditions décrites par les sources, exploitable à distance (réseau), avec des privilèges existants, requiert une interaction de l'utilisateur, affecter la confidentialité des données, l'intégrité du système et la disponibilité du service.", "basis": "CVSS 3.1"}, "mechanism": "", "mitigation": {"correction": {"available": true, "text": "Mettre à jour : selon les sources, ne sont plus concernées les versions à partir de App Installer 1.16, App Installer 1.11."}, "mitigation": {"specific": "Aucune mesure de mitigation spécifique confirmée par les sources consultées. Consultez les références officielles pour d'éventuelles mesures détaillées.", "general": ["Maintenir le produit à jour et activer les mises à jour de sécurité.", "Restreindre l'exposition réseau du service au strict nécessaire.", "Appliquer le principe du moindre privilège.", "Surveiller les journaux et les alertes de sécurité."], "specific_links": []}, "containment": {"applicable": true, "actions": ["Action recommandée par la CISA : Apply updates per vendor instructions.", "Isoler ou restreindre l'accès au service concerné.", "Restreindre les flux réseau entrants/sortants liés au composant.", "Renforcer la surveillance des journaux et des accès.", "Désactiver temporairement le composant vulnérable si l'activité le permet."]}, "note": "Priorité aux consignes officielles de l'éditeur et des références. Vérifiez toujours l'avis de sécurité avant toute intervention en production.", "official_links": [{"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "groupe": "correctif", "groupe_titre": "Correctifs et versions corrigées", "editeur": "Microsoft", "domaine": "portal.msrc.microsoft.com"}]}, "plain": {"verdict": "now", "verdict_label": "Exploité par des attaquants · à traiter aujourd'hui", "verdict_css": "now", "verdict_rank": 0, "headline": "Faille de sécurité signalée dans App Installer", "headline_is_derived": false, "action": "Mettre à jour vers App Installer 1.16, App Installer 1.11 ou plus récent, version publiée comme non concernée.", "action_kind": "update", "concerned": [{"version": "App Installer 1.16, App Installer 1.11 ou plus récent", "state": "safe", "state_label": "Non concerné", "todo": "Rien à faire. Gardez les mises à jour automatiques activées."}, {"version": "1.0.0.0", "state": "hit", "state_label": "Concerné", "todo": "Mettre à jour vers App Installer 1.16, App Installer 1.11 ou plus récent, version publiée comme non concernée."}, {"version": "Je ne connais pas ma version", "state": "unknown", "state_label": "À vérifier", "todo": "La version s'affiche généralement dans le menu « À propos » ou « Aide » du logiciel."}], "steps": [{"title": "Sauvegarder avant d'intervenir", "detail": "Une copie récente des données et de la configuration. Si votre hébergeur propose une sauvegarde en un clic, c'est le moment.", "duration": "10 min", "priority": false}, {"title": "Mettre à jour vers App Installer 1.16, App Installer 1.11 ou plus récent, version publiée comme non concernée", "detail": "C'est la correction officielle. Tant qu'elle n'est pas appliquée, les autres mesures ne sont que temporaires.", "duration": "15 à 45 min", "priority": true}, {"title": "En attendant : réduire l'exposition sur Internet", "detail": "La faille est exploitable à distance. Limiter l'accès au service depuis l'extérieur (pare-feu, filtrage d'adresses, VPN) réduit fortement le risque.", "duration": "30 min", "priority": false}, {"title": "Vérifier que vous n'avez pas déjà été touché", "detail": "Cette faille est activement exploitée. Contrôler les comptes créés récemment, les connexions inhabituelles et les fichiers modifiés depuis la date de publication.", "duration": "30 min", "priority": true}, {"title": "Confirmer que tout fonctionne encore", "detail": "Après correction : page d'accueil, connexion, et les deux ou trois fonctions dont vous vous servez tous les jours.", "duration": "10 min", "priority": false}], "exploited": true, "exploited_label": "Oui, des attaques réelles sont constatées", "fixed_label": "App Installer 1.16, App Installer 1.11 (non concernée selon les sources)", "affected_label": "1.0.0.0"}, "severity_display": "Élevée", "cvss_is_legacy": false, "risk_score_computable": true, "identifier": "CVE-2021-43890", "severity_fr": "Élevée", "epss_pct": 10.3, "source_records": [{"source": "NVD", "label": "NVD, NIST", "date_label": "Publié dans la base", "date": "2021-12-15", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-43890"}, {"source": "CVE.org", "label": "CVE.org, programme CVE", "date_label": "Publié par l'organisme CNA", "date": "2021-12-15", "url": "https://www.cve.org/CVERecord?id=CVE-2021-43890"}, {"source": "CISA", "label": "CISA KEV", "date_label": "Ajout au catalogue", "date": "2021-12-15", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890"}, {"source": "FIRST EPSS", "label": "FIRST EPSS", "date_label": "Score daté du", "date": "2026-10-06", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-43890"}], "exploit_public": true, "reseau_sans_auth": false, "exposition": "À distance, sous conditions (compte ou action d'un utilisateur)", "owasp": []}, "presentation": {"en_bref": [{"question": "Est-elle attaquée ?", "ton": "alerte", "reponse": "Oui, attaques constatées", "source": "Catalogue CISA KEV"}, {"question": "Existe-t-il un correctif ?", "ton": "bon", "reponse": "Oui : 1.16, 1.11", "source": "Versions publiées comme non concernées"}, {"question": "Comment l'attaquer ?", "ton": "neutre", "reponse": "À distance, sous conditions (compte ou action d'un utilisateur)", "source": "Vecteur CVSS publié"}, {"question": "Risque d'exploitation", "ton": "alerte", "reponse": "10,3 % sur 30 jours", "source": "Plus probable que 96 % des failles connues"}], "references": [{"cle": "correctif", "titre": "Correctifs et versions corrigées", "explication": "Les pages que les sources désignent comme correctif ou notes de version.", "items": [{"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "domaine": "portal.msrc.microsoft.com", "editeur": "Microsoft", "etiquettes": ["Correctif", "Avis de l'éditeur"], "nom": "", "lien": true, "casse": false}]}, {"cle": "avis_tiers", "titre": "Avis d'autorités et d'organismes tiers", "explication": "CERT, agences gouvernementales, bases de vulnérabilités, chercheurs.", "items": [{"url": "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html", "domaine": "thehackernews.com", "editeur": "", "etiquettes": ["Article de presse", "Avis d'un tiers"], "nom": "", "lien": true, "casse": false}, {"url": "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/", "domaine": "www.bleepingcomputer.com", "editeur": "", "etiquettes": ["Article de presse", "Avis d'un tiers"], "nom": "", "lien": true, "casse": false}, {"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890", "domaine": "www.cisa.gov", "editeur": "CISA", "etiquettes": ["Ressource gouvernementale américaine", "Ressource gouvernementale"], "nom": "", "lien": true, "casse": false}]}, {"cle": "analyse", "titre": "Analyses, tickets et discussions", "explication": "Pour comprendre le défaut : description technique, ticket, liste de diffusion.", "items": [{"url": "https://github.com/ChrisTitusTech/winutil/pull/26", "domaine": "github.com", "editeur": "GitHub", "etiquettes": ["Suivi de ticket"], "nom": "", "lien": true, "casse": false}]}, {"cle": "exploit", "titre": "Codes d'exploitation référencés", "explication": "Les sources signalent un code d'exploitation public. Par prudence, CyberAlert affiche le site qui l'héberge sans lien direct : l'information utile ici est son existence, qui rend la faille plus facile à attaquer.", "items": [{"url": "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/", "domaine": "www.microsoft.com", "editeur": "", "etiquettes": ["Code d'exploitation", "Avis de l'éditeur"], "nom": "", "lien": false, "casse": false}]}], "liens_correction": [{"url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890", "domaine": "portal.msrc.microsoft.com", "editeur": "Microsoft", "etiquettes": ["Correctif", "Avis de l'éditeur"], "nom": "", "lien": true, "casse": false, "groupe": "correctif", "groupe_titre": "Correctifs et versions corrigées"}], "nb_exploits": 1, "cvss": {"version": "3.1", "vecteur": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H", "metriques": [{"code": "AV", "nom": "Vecteur d'attaque", "valeur": "Réseau (à distance, y compris par Internet)", "brut": "N", "explication": "D'où l'attaquant doit agir."}, {"code": "AC", "nom": "Complexité de l'attaque", "valeur": "Élevée", "brut": "H", "explication": "Conditions hors du contrôle de l'attaquant."}, {"code": "PR", "nom": "Privilèges requis", "valeur": "Faibles (compte ordinaire)", "brut": "L", "explication": "Droits dont l'attaquant a besoin avant d'attaquer."}, {"code": "UI", "nom": "Interaction de l'utilisateur", "valeur": "Requise", "brut": "R", "explication": "Une victime doit-elle cliquer ou ouvrir quelque chose ?"}, {"code": "S", "nom": "Portée", "valeur": "Inchangée", "brut": "U", "explication": "L'attaque peut-elle toucher d'autres composants que celui qui est vulnérable ?"}, {"code": "C", "nom": "Confidentialité", "valeur": "Élevé", "brut": "H", "explication": "Accès à des informations protégées."}, {"code": "I", "nom": "Intégrité", "valeur": "Élevé", "brut": "H", "explication": "Modification de données ou du système."}, {"code": "A", "nom": "Disponibilité", "valeur": "Élevé", "brut": "H", "explication": "Arrêt ou ralentissement du service."}], "calculateur": "https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H", "specification": "https://www.first.org/cvss/v3.1/specification-document"}, "cvss4": null, "cwe": [], "owasp": [], "ssvc": {"lignes": [{"nom": "Exploitation", "valeur": "Exploitation active constatée", "brut": "active"}, {"nom": "Automatisable", "valeur": "Non : l'attaque ne peut pas être entièrement automatisée", "brut": "no"}, {"nom": "Impact technique", "valeur": "Total : contrôle complet du composant ou de ses informations", "brut": "total"}], "version": "2.0.3", "date": "2021-12-14", "role": "CISA Coordinator", "url": "https://www.cisa.gov/stakeholder-specific-vulnerability-categorization-ssvc"}, "chronologie": [{"date": "2021-11-16", "libelle": "Identifiant réservé", "qui": "Programme CVE"}, {"date": "2021-12-14", "libelle": "Décision SSVC publiée", "qui": "CISA"}, {"date": "2021-12-15", "libelle": "Publication de la vulnérabilité", "qui": "microsoft"}, {"date": "2021-12-15", "libelle": "Ajout au catalogue des failles exploitées", "qui": "CISA"}, {"date": "2021-12-29", "libelle": "Échéance de correction fixée par la CISA", "qui": "CISA"}, {"date": "2026-08-06", "libelle": "Dernière mise à jour de la fiche source", "qui": "Source"}, {"date": "2026-10-06", "libelle": "Calcul du score EPSS affiché", "qui": "FIRST"}], "liens_officiels": [{"nom": "NVD (NIST)", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-43890", "description": "Fiche de référence : CVSS, CPE, références étiquetées."}, {"nom": "CVE.org", "url": "https://www.cve.org/CVERecord?id=CVE-2021-43890", "description": "Enregistrement officiel publié par l'organisme qui a attribué l'identifiant."}, {"nom": "CISA KEV", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890", "description": "Entrée du catalogue des failles activement exploitées."}, {"nom": "FIRST EPSS", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-43890", "description": "Score de probabilité d'exploitation du jour."}, {"nom": "OSV.dev", "url": "https://osv.dev/vulnerability/CVE-2021-43890", "description": "Paquets open source concernés et versions corrigées."}, {"nom": "GitHub Advisory Database", "url": "https://github.com/advisories?query=CVE-2021-43890", "description": "Avis de sécurité des dépendances logicielles."}], "produits": [{"vendor": "Microsoft", "product": "App Installer", "ranges": ["avant 1.16", "avant 1.11"], "first_unaffected": ["1.16", "1.11"], "source": "NVD"}], "notes_kev": ["https://nvd.nist.gov/vuln/detail/CVE-2021-43890"]}, "consulted_at": "2026-10-07T05:39:50.354541+00:00"}